In‐Situ Hydrogen‐Bond Tailoring To Construct Ultrathin Bi₂O₂O/Bi₂O₂(OH)(NO₃) Nanosheets: Interactive CO₂RR Promotion and Bismuth‐Oxygen Moiety Preservation

AbstractBismuth–oxygen moieties are beneficial for high‐efficiency electrochemical CO2 reduction (CO2RR) to produce formate; however, preserving bismuth‐oxygen moieties while applying a cathodic potential is challenging. This work reports the preparation of ultrathin Bi2O2O/Bi2O2(OH)(NO3) nanosheets (BiON‐uts) by in‐situ tailoring of hydrogen bonds in a Bi2O2(OH)(NO3) precursor. The BiON‐uts exhibits a formate faradaic efficiency of 98 % with higher partial current density than that of most reported bismuth‐based catalysts. Mechanistic studies demonstrate that the ultrathin nanosheet morphology facilitates ion‐exchange between BiON‐uts and the electrolyte to produce Bi2O2CO3 as intermediate, and adsorption of CO2 with surface Bi2O2O. DFT calculations reveal that the rate‐limiting first electron transfer is effectively improved by the high electron affinity of Bi2O2CO3. More importantly, high‐efficiency CO2RR in turn protects the bismuth–oxygen moieties from being reduced and thus helps to maintain the excellent CO2RR activity. This work offers an interactive mechanism of CO2RR promotion and bismuth–oxygen moiety preservation, opening up new opportunities for developing high‐performance catalysts.